A wall cloud is a lowering of the cloud base in a thunderstorm, preceding the formation of a tornado. Wall clouds exhibit characteristics in their formation, rotation, shape, and associated wind patterns. Wall clouds develop as part of severe thunderstorms and are linked to the storm’s updraft. Understand the features of wall clouds to recognize these dangerous weather phenomena.
Wall clouds differ from shelf clouds in aspects. Wall clouds form in the rear sector of storms and are associated with strong updrafts and inflow. Wall clouds are lower in size and drop closer to the ground from storm cells. Shelf clouds stretch across horizons and reach heights over 10,000 meters (32,808 feet). Wall clouds rotate around a vertical axis, indicating tornado formation.
Wall clouds have an appearance that sets them apart from cloud formations. Wall clouds look like hanging cloud formations at the base of thunderstorms, extending several kilometers. Wall clouds take on an appearance, with a cloud base 0.62-1.24 miles above the ground. The hanging cloud formation extends 500-2,000 meters from the storm base to the ground. Wall clouds exhibit an appearance stretching 5.0-10.0 kilometers (3.1-6.2 miles) in length and 1.0-5.0 kilometers (0.6-3.1 miles) in width. Wall clouds display a tint when associated with hail or heavy rain.
Wall clouds are parts of severe thunderstorms known as supercells. Wall clouds serve as precursors to tornado formation, consisting of low-hanging, rotating cloud bases that extend miles into the sky. Wall cloud formation occurs when updrafts cause air to rise, condense, and form a lowered, rotating cloud base. Wall cloud bases exhibit a roiling appearance due to updrafts and inflow. Wall cloud rotation is driven by a mesocyclone, with rotation speeds reaching up to 100 meters per second (328.08 feet per second). Studies show that up to 90% of tornadoes develop from wall clouds. Wall clouds contribute to storm dynamics by channeling warm, moist air into the storm’s core.
What is a wall cloud?
A wall cloud is a localized lowering of the cloud base beneath a cumulonimbus cloud, associated with potential tornado formation. Wall clouds form when thunderstorms produce rotating updrafts called mesocyclones. Meteorologists classify wall clouds as precursors to potential tornado formation. Storm chasers seek out wall clouds to identify areas of possible tornado development. Wall clouds exhibit low-hanging cloud bases extending miles in front of parent thunderstorms. The National Weather Service utilizes wall cloud observations in issuing thunderstorm and tornado warnings.
Wall clouds possess a distinctive cylindrical or wedge shape. The cloud base extends 1-2 kilometers (0.62-1.24 miles) above the ground, lower than the surrounding storm structure. Wall clouds form at the base of cumulonimbus clouds, marking areas of strong updraft and rotation within storms. These formations are smaller and more compact than shelf clouds, spanning several miles in front of parent thunderstorms.
Wall cloud formation occurs through rotating updrafts called mesocyclones. Thunderstorm updrafts cause water droplets and ice crystals to condense and grow, creating towering clouds. Inflow of warm, moist air into storm updrafts contributes to wall cloud development. Temperature differences between the updraft and surrounding air influence the cloud’s shape and behavior.
Wall clouds exhibit features that distinguish them from other cloud formations. Rotation patterns are rapid, indicating the presence of a mesocyclone. The rain-free base of a wall cloud contrasts with the surrounding precipitation areas. Sky areas appear beneath wall clouds, emphasizing their unique structure.
Wall clouds play a role in storm dynamics and severe weather prediction. These formations indicate tornado development when rotation extends to the ground. Meteorologists and storm chasers use wall cloud observations to assess the likelihood of tornado formation. The National Weather Service incorporates wall cloud reports into their thunderstorm and tornado warning systems. Wall clouds generate various severe weather phenomena, including hail, winds, and tornadoes.
Do wall clouds produce tornadoes?
Wall clouds produce tornadoes, with 25% of wall clouds generating tornadoes when persistent rotation and strong updrafts are present. Persistent rotating wall clouds are an indication of potential tornado formation. Tornadogenesis occurs within wall clouds due to their updrafts and rotation. Wall clouds form at the base of thunderstorms, lowering and becoming dense as the mesocyclone develops. NOAA reports indicate that tornadoes form within 30-60 minutes after a wall cloud appears. Warning signs of a tornado-producing wall cloud include a dark greenish tint, loud continuous roar, and funnel clouds.
What is the difference between wall clouds and shelf clouds?
The difference between wall clouds and shelf clouds is that wall clouds form in the updraft area at the leading edge of a thunderstorm and tend to rotate, while shelf clouds form in the outflow area behind the storm’s leading edge and are associated with downdrafts. Wall clouds rotate around a vertical axis, indicating the presence of a tornado. Shelf clouds move away from the storm’s updraft area and signify wind shear. Wall clouds appear as hanging clouds with bases and flat tops. Shelf clouds have flat bases and rounded tops, forming an anvil shape. Both cloud formations indicate weather conditions, including precipitation and potential tornadic activity.
The difference between wall clouds and shelf clouds is explained in the table below.
| Aspect | Wall Clouds | Shelf Clouds |
| Location in Storm | Form 3-10 km (1.9-6.2 miles) behind the leading edge of the storm, in the updraft area at the rear of the storm | Form at the leading edge of the storm, in the outflow area, typically 1-5 km (0.6-3.1 miles) ahead of the storm's center |
| Formation | Associated with updrafts of 10-50 m/s (36-180 km/h or 22-112 mph) and inflow of 5-20 m/s (18-72 km/h or 11-45 mph) | Associated with downdrafts of 5-20 m/s (18-72 km/h or 11-45 mph) and outflow of 10-50 m/s (36-180 km/h or 22-112 mph) |
| Shape | Cauliflower shape with cloud bases at 500-2000 meters (1640-6562 feet) and flat tops at 2000-5000 meters (6562-16404 feet) | Elongated and wavy shape with flat bases at 1000-3000 meters (3281-9843 feet) and rounded tops at 3000-6000 meters (9843-19685 feet) |
| Rotation | Rotate around a vertical axis at 10-50 degrees per second, indicating tornado potential | Rotate around a horizontal axis at 1-10 degrees per second, indicating wind shear |
| Height & Size | Typically 1-5 km (0.6-3.1 miles) wide and 1-2 km (0.6-1.2 miles) tall, hanging 500-2000 meters (1640-6562 feet) above the ground | Can stretch 10-50 km (6.2-31 miles) across the horizon and reach heights over 10,000 meters (32,808 feet) |
| Weather Conditions | Indicate potential tornadic activity, with wind speeds of 50-200 km/h (31-124 mph) and hail diameters of 1-5 cm (0.4-2 inches) | Indicate strong straight-line winds of 50-150 km/h (31-93 mph) and severe weather with heavy rain and hail |
Shelf clouds develop at the leading edge of thunderstorms, linked to downdrafts and outflow. Wall clouds are smaller in size, dropping closer to the ground from storm cells. Shelf clouds are expansive, stretching across entire horizons and reaching heights over 32,808 feet (10,000 meters). Wall clouds appear with “cauliflower” shapes and lowered cloud bases. Shelf clouds have an elongated appearance with rolling or wavy shapes and flat bases.
Shelf clouds rotate on a horizontal axis, signifying wind shear and outflow boundaries. Wall clouds pose risks of tornadoes due to their association with rotating updrafts. Shelf clouds produce strong straight-line winds, causing damage over areas. Meteorologists examine these characteristics to identify wall clouds versus shelf clouds, providing warnings to the public for severe weather events.
What is the difference between a wall cloud and a funnel cloud?
The difference between a wall cloud and a funnel cloud is that wall clouds form at the base of thunderstorms and may exhibit rotation, while funnel clouds always rotate and extend downward from the thunderstorm base with a cone-shaped appearance. Wall clouds develop within 10-15 kilometers of the ground. Wall clouds are associated with the updraft within the storm. Funnel clouds extend downward from the thunderstorm base within 1-2 kilometers of the ground. Wall clouds appear as lowered cloud formations, often several kilometers wide. Funnel clouds have a narrow, tapering shape that extends from the thunderstorm base.
Wall clouds and funnel clouds differ in their location and formation process. Wall clouds form at the base of thunderstorms from rising air within the storm. The rising air causes water droplets and ice crystals to condense, creating a cloud formation. Funnel clouds extend downward from the thunderstorm base, forming from rotating wall clouds. A wall cloud signifies a strengthening mesocyclone, which leads to funnel cloud development.
Rotation and shape are distinguishing factors between wall clouds and funnel clouds. Wall clouds exhibit rotation, indicating a strengthening updraft. Wall clouds appear as lowered cloud formations, kilometers in width, and look like a hanging cloud or a series of clouds. Scud clouds, which are low-level clouds, accompany wall clouds. Funnel clouds rotate and have a cone-shaped or needle appearance. Funnel clouds display a tapering shape that extends from the thunderstorm base.
Ground contact and tornado potential vary between wall clouds and funnel clouds. Wall clouds do not touch the ground and remain suspended in the air. While wall clouds lead to tornadoes, their presence does not guarantee tornado formation. Funnel clouds extend towards the ground but do not make contact. A funnel cloud becomes a tornado if it touches the ground. Severe thunderstorms produce both wall clouds and funnel clouds, with funnel clouds indicating a rotating mesocyclone that has potential to produce a tornado.
What do wall clouds look like?
Wall clouds look like hanging cloud formations that appear at the base of thunderstorms and are associated with potential tornado formation. Wall clouds accompany heavy rain, hail, or snow during thunderstorms. Cumulonimbus clouds feature wall clouds at their base, extending several kilometers. Wall clouds have an anvil-shaped appearance and signify the presence of rotating updrafts called mesocyclones. Murus clouds, known as wall clouds, form but are smaller and less intense than cumulonimbus clouds.
Wall clouds develop beneath the rain-free base of thunderstorms. These formations appear as localized and abrupt lowerings of the cloud base. Wall clouds take on a wedge-shaped appearance. The lower-hanging cloud formation extends 1,640.42-6,561.68 feet (500-2,000 meters) from the storm base to the ground. Wall clouds exhibit an appearance stretching 3.1-6.2 miles (5-10 kilometers) in length and 0.6-3.1 miles (1-5 kilometers) in width.
Wall clouds display several distinctive features. Drooping cloud structures hang down from the cloud mass. Pouches form as localized lowerings, indicating areas of strong inflow and updraft. Wall clouds exhibit a greenish tint when associated with hail or heavy rain. Rotating wall clouds spin at speeds up to 100 km/h (62 mph), signaling tornado formation. Funnel clouds extend from the wall cloud base towards the ground in certain cases. Wall clouds maintain their lowering for extended periods, serving as important severe storm indicators for meteorologists.
How do wall clouds form?
Wall clouds form when warm, moist air rises, creating an updraft that converges with cooler air, resulting in a rotating mesocyclone within a supercell thunderstorm. Rising air creates an area of low pressure near the ground. Entrainment of surrounding air strengthens the updraft, creating a self-sustaining cycle. Convergence with air forces the air upward, forming the wall cloud. Wall clouds extend miles wide and tall within supercell thunderstorms. Strengthening mesocyclones develop into scale circulations, reaching miles into the sky.
Wall clouds develop through a series of atmospheric processes. Warm, moist air rises and creates a low-pressure area near the ground. Rising air converges with air masses and overpowers denser rain-cooled air, forming a rotating zone. Entrainment occurs as the rising air pulls in surrounding air, strengthening the updraft. The rising air encounters colder air at higher altitudes, causing it to cool and condense into water droplets.
Cloud formation begins as the cooled air continues to rise and condense. A rotating lowering develops beneath the cumulonimbus cloud, reaching over 32,808.4 feet (10,000 meters). The wall cloud establishes itself as a feature of the supercell thunderstorm. Wall clouds form a rain-free base without precipitation, instead featuring a rotating, lowering cloud formation. The lowering of the cloud base is caused by the release of heat during condensation, creating a descending zone.
Wall cloud heights range from 1-2 kilometers (0.62-1.24 miles) above ground. Wall cloud rotation speeds reach 10-50 meters per second (22-112 miles per hour). The influx of warm, rising air feeds the wall cloud, maintaining its structure and rotation. Wall clouds do not produce precipitation themselves but serve as a precursor to tornado formation under conditions.
What forms a rotating wall cloud?
A rotating wall cloud forms when warm, moist air converges, rises, and interacts with downdrafts and inflow, creating a rotating structure at the base of a thunderstorm. Thunderstorms provide conditions for wall cloud formation. Warm, moist air near the surface rises, creating an area of low pressure. Downdrafts from the storm spread out upon reaching the ground, forcing warm air to rise. Air entrainment fuels the rotation of the wall cloud as it develops. Inflow of warm, moist air sustains the rotating structure at the base of the storm.
Warm, moist air converges near the surface, creating an area of low pressure. The warm air rises, forming an updraft that becomes strong. Updraft velocities reach 10-20 m/s (22.4-44.7 mph) as the storm intensifies. Entrainment occurs as the updraft strengthens, pulling in surrounding air and fueling development. Rotation develops due to wind shear, with speeds of 20-40 m/s (45-89 mph) in the lowest 1 km (0.62 miles) contributing to formation. A mesocyclone forms if rotation becomes strong, characterized by rotation speeds ranging from 10-50 m/s (22.4-112.0 mph).
The cumulonimbus cloud base lowers as the mesocyclone forms, reaching heights of 1640.42-3280.84 ft above ground. Cloud base lowering continues as the updraft intensifies, extending towards the ground in a wall appearance. Rain-cooled air from downdrafts interacts with warm inflow, creating a zone of rotation near the surface. Warm air continues to flow into the strengthening storm, with inflow speeds exceeding 31.07 mph (50 km/h). The storm updraft strengthens, reaching velocities of 50-100 m/s ( 164-328 ft/s) in mature rotating wall clouds.
The vertical axis of rotation extends from the storm base to the ground, forming the developed rotating wall cloud. Rotating wall clouds have diameters ranging from 0.62-6.21 miles (1-10 km) and heights of 0.62-3.11 miles (1-5 km) above ground. Updrafts, rain, and hail are associated with rotating wall clouds. Rotation velocities within the wall cloud reach 10-20 m/s (22.4-44.7 mph). Rotating wall clouds signal storms with tornado potential, though not all produce tornadoes.
Is a wall cloud part of a storm?
Yes, a wall cloud is part of a storm, specifically a severe thunderstorm known as a supercell, and serves as a precursor to tornado formation. Wall clouds consist of a low-hanging, rotating cloud base extending miles into the sky. Supercells are characterized by wall clouds and their rotating structure. Meteorologists consider wall clouds indicators of potential tornado formation. Storms containing wall clouds pose risks for severe weather events. Forecasters monitor wall clouds to predict the likelihood of tornadoes.
Wall cloud formation occurs when strong updrafts within thunderstorms cause air to rise. Rising air condenses and forms a lowered, rotating cloud base beneath the storm structure. Wall clouds extend from the storm’s base to thousand feet high, appearing as a wall-like feature. The structure of a wall cloud is characterized by a lowered base, 0.62-1.86 miles (1-3 km) above the ground, with an oval shape. Wall cloud bases exhibit a roiling appearance due to the intense updrafts and inflow.
Wall cloud rotation is driven by the mesocyclone, a rotating column of air within the thunderstorm. Rotation speeds in wall clouds reach up to 100 meters per second (328.08 feet per second), creating a spinning cloud structure. Wall clouds are associated with tornado formation, with studies showing that up to 90% of tornadoes develop from wall clouds. Meteorologists and storm chasers monitor wall clouds as indicators of potential tornado development. Wall clouds serve as features in severe weather forecasting, alerting forecasters to the likelihood of tornadic activity.
Wall clouds are components of supercell thunderstorms, marking areas of intense updrafts and rotation. Supercells are characterized by the presence of wall clouds, which contribute to the storm dynamics by channeling warm, moist air into the storm’s core. Wall clouds are accompanied by other severe weather phenomena, including hail up to 3.94 in (10 cm) in diameter and winds exceeding 62.14 mph (100 km/h). The presence of a wall cloud in a thunderstorm indicates an organized and dangerous weather system capable of producing significant severe weather events.
What is a circular wall cloud?
A circular wall cloud is a cloud base that forms beneath a supercell thunderstorm and is associated with severe weather and potential tornado development. Circular wall clouds extend kilometers in diameter. Mesocyclones within thunderstorms cause clouds to rotate and take on circular shapes. Lowering cloud bases characterize circular wall clouds, forming in the vicinity of mesocyclones.